MDM4 and Familial prostate cancer: To test the hypothesis that combined inhibition of MDM2 and MDMX suppresses cell growth of prostate cancer cells, we examine the effect of various MDM2/MDMX inhibitors (Supplementary Figure 2) on cell proliferation of three different prostate cancer cell lines (Figure 2A): LNCaP cells are responsive to androgen and contain the wild-type p53 gene.